File repair method and file repair device for user equipment

ABSTRACT

In a file repair method for a user equipment (UE), the UE receives a target file multicasted by a network side in a file download transmission (FDT) manner. The method includes transmitting, by the UE, a multicast attempt repair request for the target file to the network side in a first time period after determining that the target file needs to be repaired, where the first time period does not exceed a time period of a Back-off time of a current session, receiving, by the UE, a feedback message transmitted by the network side, where the feedback message instructs the UE to perform multicast repair, and performing, by the UE, the multicast repair on the target file in response to the received feedback message.

CROSS REFERENCE TO RELATED APPLICATION

This U.S. non-provisional application claims priority under 35 U.S.C. §119 to Chinese Patent Application No. 202111570594.6 filed Dec. 21,2021, the disclosure of which is incorporated by reference herein in itsentirety.

TECHNICAL FIELD

Embodiments of the inventive concept generally relate to multimediabroadcast and multicast, and in particular, to a file repair method anda file repair device for a user equipment (UE).

DISCUSSION OF RELATED ART

Multimedia Broadcast/Multicast Service (MBMS) is an importantcharacteristic introduced by the 3GPP (3rd Generation PartnershipProject) organization in the R6 version. It is a point-to-multipointservice for achieving simultaneous transmission of data from a datasource to multiple User Equipments (UEs) within a specific range, andprovides multimedia services to a large number of UEs with the sameneeds with fewer resources at the same time, thus sharing network(including core network and access network) resources. EvolvedMultimedia Broadcast/Multicast Service (eMBMS) is an evolution of MBMSin Long Term Evolution (LTE).

MBMS transmission methods are mainly divided into four categories: FileDownload Transmission (FDT), streaming media transmission, groupcommunication transmission, and transparent transmission. To supplementor enhance transmission characteristics of eMBMS, Associated DeliveryProcedure (ADP) is also designed in the protocol, and ADP includes filerepair. The file repair refers to a supplementary strategy for repairinga file with lost fragments or damaged in FDT, which mainly includesunicast repair and multicast repair (multicast herein collectivelyrefers to broadcast service and multicast service).

After an expiration time of a data transmission session is reached, a UEmay trigger a file repair process if a file download fails. The filerepair process includes the UE first determines whether a network sidesupports a unicast repair mechanism. If the network side supports theunicast repair mechanism, it may monitor an In-band message to determinewhether to trigger multicast repair before a Back-off Time expires. Ifthe In-band message that triggers the multicast repair is not monitoredafter the Back-off Time expires, the UE may be triggered to transmit afile repair request to the network side to perform the unicast repairprocess. If the UE receives, from the network side, a Uniform ResourceIdentifier (URI) to redirect the multicast repair after transmitting thefile repair request, the UE performs the multicast repair process.

In the above file repair process, when the network side supports theunicast repair mechanism, whether the UE performs the multicast repairdepends on the monitored In-band message. Whether the network side willtransmit the In-band message to trigger the UE to start the multicastrepair may require a certain amount of judgment time, and the UE thattransmits the file repair request may only adopt the unicast repairbefore the network side makes a decision. For example, the network sidemay decide to start the multicast repair based on the number of UEstransmitting repair requests for the same file exceeding a threshold. Inthis way, if the number of UEs transmitting the file repair requests hasnot reached the threshold after these UEs transmit the file repairrequests to the network side, the network side will not trigger theseUEs to enter the multicast repair process, and these UEs may onlyperform the unicast repair process first. If the number of UEs thattrigger this file repair is enough so that the condition of themulticast repair is met, the network side may then decide to perform themulticast repair. Repairing the file in this way will cause a largeamount of downlink data and waste of network resources.

SUMMARY

According to an embodiment of the inventive concept, a file repairmethod for a user equipment (UE) is provided. The UE receives a targetfile multicasted by a network side in a file download transmission (FDT)manner. The method includes transmitting, by the UE, a multicast attemptrepair request for the target file to the network side in a first timeperiod after determining that the target file needs to be repaired,where the first time period does not exceed a time period of a Back-offtime of a current session, receiving, by the UE, a feedback messagetransmitted by the network side, where the feedback message instructsthe UE to perform multicast repair, and performing, by the UE, themulticast repair on the target file in response to the received feedbackmessage.

According to an embodiment of the inventive concept, a file repairmethod for a first UE is provided. The first UE receives a target filemulticasted by a network side in a file download transmission (FDT)manner. The method includes receiving, by the network side, multicastattempt repair requests for the target file transmitted by UEs includingthe first UE, performing, by the network side, statistics on thereceived multicast attempt repair requests for the target file todetermine whether to perform multicast repair on the target file beforea second time period expires, where the second time period is less thana time period of a Back-off time of a current session, and transmitting,by the network side, a feedback message to the UEs in a multicast areaif it is determined to perform the multicast repair on the target file,where the feedback message instructs the first UE to perform themulticast repair on the target file.

According to an embodiment of the inventive concept, a file repairdevice for a user equipment (UE) is provided. The UE receives a targetfile multicasted by a network side in a file download transmission (FDT)manner. The device includes a requesting circuit configured to transmita multicast attempt repair request for the target file to the networkside in a first time period after determining that the target file needsto be repaired, where the first time period does not exceed a timeperiod of a Back-off time of a current session, a receiving circuitconfigured to receive a feedback message transmitted by the networkside, where the feedback message instructs the UE to perform multicastrepair, and a repairing circuit configured to perform the multicastrepair on the target file in response to the received feedback message.

According to an embodiment of the inventive concept, a file repairdevice for a first UE is provided. The first UE receives a target filemulticasted by a network side in a file download transmission (FDT)manner. The device includes a receiving circuit configured to receivemulticast attempt repair requests for the target file transmitted by UEsincluding the first UE, a decision circuit configured to performstatistics on the received multicast attempt repair requests for thetarget file to determine whether to perform multicast repair on thetarget file before a second time period expires, where the second timeperiod is less than a time period of a Back-off time of a currentsession, and a transmitting circuit configured to transmit a feedbackmessage to the UEs in a multicast area if it is determined to performthe multicast repair on the target file, where the feedback messageinstructs the first UE to perform the multicast repair on the targetfile.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the inventive concept will become moreapparent by describing in detail embodiments thereof with reference tothe accompanying drawings.

FIG. 1 shows a flowchart of a file download transmission (FDT) filetransmission method in a multimedia broadcast/multicast service in priorart.

FIG. 2 shows a flowchart of a file repair method on a user equipment(UE) side according to an embodiment of the inventive concept.

FIG. 3 shows a flowchart of a file repair method on a network sideaccording to an embodiment of the inventive concept.

FIG. 4 shows a timing diagram of a file repair method of a UE accordingto an embodiment of the inventive concept.

FIG. 5 shows a block diagram of a file repair device on a UE sideaccording to an embodiment of the inventive concept.

FIG. 6 shows a block diagram of a file repair device on a network sideaccording to an embodiment of the inventive concept.

FIG. 7 shows a block diagram of a decision unit according to anembodiment of the inventive concept.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the inventive concept provide a file repair method and afile repair device for a user equipment (UE), which transmit a multicastattempt repair request for a target file to a network side in advance,so that the network side may collect the repair request for the targetfile from the UE in advance, and then may quickly decide whether toperform multicast repair. Especially in the case that the multicastrepair is required, the multicast repair is performed on the target filefirst, which may reduce downlink unicast traffic, reduce dependence on alarge number of file repair servers, and greatly reduce consumption ofbandwidth and software and hardware resources.

Embodiments of the inventive concept will be described more fullyhereinafter with reference to the accompanying drawings. Like referencenumerals may refer to like elements throughout this application.

FIG. 1 shows a flowchart of a file download transmission (FDT) filetransmission method in a multimedia broadcast/multicast service in priorart.

As shown in FIG. 1 , in prior art, after an expiration time of a datatransmission session of FDT in multimedia broadcast/multicast service(MBMS) is reached, a session time of MBMS expires, a schedule time of afile expires, or a UE fails to download a target file, a repair processof the target file may be triggered. The repair process includes:

Operation S101: The UE determines whether a network side supports aunicast repair mechanism.

The UE receives a broadcast message transmitted by the network side, andthe broadcast message carries information indicating whether the networkside supports unicast repair or multicast repair.

Operation S102: If the UE determines that the network side does notsupport the unicast repair mechanism, it continues to determine whetherthe network side supports a multicast repair mechanism. If the networkside supports the multicast repair mechanism (S102: Y), the repairprocess skips to operation S109 to perform the multicast repair;otherwise (S102: N), the repair process ends.

Operation S103: If the UE determines that the network side supports theunicast repair mechanism, the UE selects a server address for theunicast repair from a file repair server list of Associated DeliveryProcedure (ADP), and starts a Back-off timer.

Operation S104: Before the Back-off timer expires, the UE monitors anIn-band message transmitted by the network side to determine whether totrigger the multicast repair; if the UE receives the In-band messagethat triggers the multicast repair (S104: Y), the repair process skipsto S109 to perform the multicast repair.

Operation S105: If the UE does not receive the In-band message thattriggers the multicast repair (S104: N), the UE determines whether theBack-off timer expires. If the Back-off timer does not expire (S105: N),the repair process returns to operation S104 to continue monitoring; ifthe Back-off timer expires (S105: Y), the repair process performsoperation S106.

Operation S106: The UE transmits a unicast repair request to the networkside, where the unicast repair request carries the server address forthe unicast repair selected by the UE, basic information of the targetfile, and lost information of the target file.

Operation S107: The UE receives a feedback message transmitted by thenetwork side, and determines whether a multicast Uniform ResourceIdentifier (URI) is redirected, and if so (S107: Y), the repair processskips to operation S109 to perform the multicast repair.

Operation S108: If the multicast URI is not redirected (S107: N), theunicast repair is performed.

For the unicast repair in the present embodiment, the UE receives aunicast repair message transmitted by the network side.

If the unicast repair message carries unicast repair data, the UErepairs the target file according to the unicast repair data, and theunicast repair process ends with a successful repair.

If the unicast repair message indicates that the server address carriedin the unicast repair request is not available, the UE selects a newserver address from the server list of the ADP again.

The UE re-transmits a new unicast repair request to the network side.The new unicast repair request carries the new server address. If therepair data is successfully received from the network side, the processends; otherwise, the UE continues to select a new server address, untilall server addresses in the server list of the ADP are tried.

Operation S109: The UE performs the multicast repair.

For example, the UE opens a new multicast session, or receives therepair data by using the original session to complete the multicastrepair.

In view of the above process, in the case that the multicast repair isrequired, and before the network side makes a decision for the multicastrepair, the UE that transmits the unicast repair request first needs toperform the unicast repair to obtain the repair data from the networkside. After the network side makes the decision for the multicastrepair, the network side transmits the multicast repair data again,which causes a waste of network resources.

Based on the above problems, the inventive concept proposes a filerepair method for the UE. First, a file repair request (a multicastattempt repair request) transmitted by the UE to the network side isadvanced to the Back-off time, and the network side makes a statisticaldecision on received file repair requests before the Back-off time,prioritizes whether to perform the multicast repair, and if a multicastrepair condition is met, directly transmits a feedback message to theseUEs, instructing these UEs to perform the multicast repair on the targetfile. In other words, in embodiments of the inventive concept, when themulticast repair condition is met, the multicast repair is performedfirst, which eliminates the need for the unicast repair of some UEs andreduces the waste of network resources.

FIG. 2 shows a flowchart of a file repair method on a user equipment(UE) side according to an embodiment of the inventive concept. The UEreceives a target file multicasted by a network side in a file downloadtransmission (FDT) manner, and the file repair method specificallyincludes:

Operation S201: After determining that the target file needs to berepaired, the UE transmits a multicast attempt repair request for thetarget file to the network side in a first time period.

It may be understood that the target file usually refers to a multimediaservice involved in a Multimedia Broadcast/Multicast Service (MBMS)service, and multicast repair may be understood as repairing in abroadcast or multicast way (Broadcast/Multicast Repair).

Herein, the multicast attempt repair request carries basic informationand lost information of the target file. The basic information of thetarget file includes a name of the target file or an ID of the targetfile, and the lost information of the target file may include rangeinformation of symbols lost by the UE.

Herein, the first time period does not exceed a time period of aBack-off time.

In the existing technical solution, when the Back-off time expires, ifthe UE has not received an instruction of the network side to performthe multicast repair, the UE transmits a unicast repair request for thetarget file to the network side. On the other hand, in embodiments ofthe inventive concept, the multicast attempt repair request for thetarget file is transmitted to the network side in advance, so that thenetwork side may collect a repair request for the target file from theUE in advance, and then may quickly decide whether to perform themulticast repair, especially in the case that the multicast repair isrequired. As such, the multicast repair is performed on the target filefirst.

Preferably, the first time period does not exceed the time period of anOffset time.

To ensure timeliness of repairing the target file, the multicast attemptrepair request may be set to be transmitted before the Offset time, soas to ensure that the UE may still perform the unicast repair in timeafter the network side makes a unicast repair decision.

For example, to avoid instantaneous uplink request load to the network,each UE may calculate a random value Random Attempt Time according tothe Offset time to ensure that attempt requests of UEs in a multicastarea are distributed as evenly as possible in an entire interval of theOffset Time. Each UE may transmit the multicast attempt repair requestto the network side through an HTTP request when this Random AttemptTime is reached. To be backward compatible with the file unicast repairsolution of the R14 version of eMBMS 26.346, the request may carry anattempt flag bit (where 0 is an original repair request and 1 is anattempt request). The attempt flag bit is 1 for inquiring the networkside whether to perform the multicast repair on the target file.

Operation S202: The UE receives a feedback message transmitted by thenetwork side, where the feedback message is used to instruct the UE toperform the multicast repair.

According to the received multicast attempt repair requests, the networkside decides whether to perform the multicast repair after statisticalanalysis, and transmits a result back to the UE through an HTTP response(e.g., the feedback message) or In-band transmission.

If the network side decides not to perform the multicast repairaccording to the received multicast attempt repair requests after thestatistical analysis, the UE may receive a first feedback messagetransmitted by the network side, and the first feedback message is usedto instruct the UE to wait for a multicast decision instruction from thenetwork side. By configuring the first feedback message, it is possibleto wait before the decision of the multicast repair has not been madeinstead of directly performing the unicast repair, thus performing themulticast repair first and reducing downlink unicast traffic.

The feedback message received by the UE from the network side instructsthe UE to perform the multicast repair. To minimize an overhead ofdownlink network transmission, the feedback message may only feed back aflag bit to indicate a manner in which the UE performs the target filerepair.

For example, the flag bit may include a File Download Transmission (FDT)update flag instructing the UE to receive multicasted repair data basedon a current download session.

In addition, the flag bit may also include a session descriptionprotocol (SDP) update flag instructing the UE to receive multicastedrepair data in a new session.

For example, the flag bit “multi Flag” may be defined in the HTTPresponse as follows:

-   000 indicates to use a default repair process and continue to    observe In-band ADP updates;-   001 indicates to perform the multicast repair in a current session    and pay attention to receiving information by using FDT updates;-   002 indicates to perform the multicast repair in the current session    and return an FDT message URL or FDT message;-   003 indicates to receive data in a new file repair session and pay    attention to In-band SDP updates; and-   004 indicates to receive data in a whole new file repair session and    return an SDP message URL or SDP message.

Operation S203: The UE performs the multicast repair on the target fileaccording to the received feedback message.

Before expiration of the Back-off time, if the multi Flag carried in thereceived first feedback message is 000, the UE continues to wait; afterthe expiration of the Back-off time, if the UE has not received thefeedback message from the network side, operations S106-S109 shown inFIG. 1 are performed.

If the received feedback message indicates multicast repair, forexample, if the multi Flag is any one of 001-004, the multicast repairis started and performed in the manner indicated by the multi Flag.

For example, if the multi Flag is 001, the UE updates relevantparameters (such as Offset time) of the current session according to theFDT information received in the band, and uses the updated currentsession to perform the multicast repair. If the multi Flag is 002, theUE uses HTTP to receive the FDT message URL or FDT message, updates therelevant parameters of the current session according to the FDT messageor by using the FDT message URL to unicast request the FDT message, anduses the updated current session to perform the multicast repair. If themulti Flag is 003, the UE obtains the repair session information throughthe In-band SDP message, establishes a new file repair session with thenetwork side based on the obtained repair session information, andprepares to receive the multicast repair data packet transmitted by thenetwork side. If the multi Flag is 004, the UE may receive the SDPmessage URL or SDP message. If the SDP URL is received, the UE unicastrequests the network side to transmit the SDP message according to theSDP URL, and then the UE uses the SDP message information to establish anew file repair session with the network side, prepares to receive therepair data packets multicasted by the network side, and performsForward Error Correction (FEC) repair when the UE receives enoughsymbols.

If the multicast repair of the target file fails, the UE performs theunicast repair of the target file, and performs operations S106-S109described above. By performing the unicast repair after the multicastrepair fails, it is possible to focus on the multicast repair andsupplement by the unicast repair to ensure a final file repair successrate, which has better compatibility and robustness.

FIG. 3 shows a flowchart of a file repair method on a network sideaccording to an embodiment of the inventive concept. This embodiment isperformed by the network side, which may be understood as BroadcastMulticast Service Center (BM-SC), which is located in a core network andused to provide and manage multimedia broadcast/multicast services(MBMS). The method includes:

Operation S301: The network side receives multicast attempt repairrequests transmitted by UEs.

Operation S302: Before a second time period expires, the network sideperforms statistics on the received multicast attempt repair requests,and determines whether to perform multicast repair or unicast repair ona target file.

Operation S303: The network side transmits a feedback message to theUEs, where the feedback message is used to instruct the UEs to performthe multicast repair.

The second time period is a time period during which the network sidemakes a decision and transmits the feedback message, and is a timeperiod of an Offset time of a current session plus a preset time period.For example, it may range from the Offset Time to the Offset Time +Multicast Repair Offset Time. The Multicast Repair Offset Time is usedas a buffer time for the network side feeding back the multicast repairdecision.

For example, the UE side has a slight delay compared with the Back-offTime in prior art, e.g., Back off Time = the Offset Time + the MulticastRepair Offset Time + Random Time Period.

For example, the network side may use whether the number of UEs thathave transmitted the multicast attempt repair requests reaches athreshold as a judgment condition for starting the multicast repair. Ifthe number of UEs transmitting the multicast attempt repair requestsreaches the threshold, the multicast repair is determined.

The condition of whether the number of UEs reaches the threshold issimple and effective, but it is more sensitive to the number of UEs, andthe setting of the threshold has a greater impact on making thedecision. Based on this, the network side may also predict whether tostart the multicast repair through a machine learningmulti-classification model, which helps to reduce an influence ofparameters, such as the threshold, on making the decision and tooptimize a method for making the decision on the network side.

For example, in operation S302, after the network side determines toperform the multicast repair on the target file, it may also determine amulticast repair strategy for the target file. The multicast repairstrategy includes multicast repair data and a multicast repair method.

Herein, the multicast attempt repair request includes lost informationof the target file; the lost information is different for different UEs.The network side, based on the multicast attempt repair requestsreceived from multiple UEs, performs statistics on the lost informationcarried in the multicast attempt repair requests, so as to determinemulticast repair information. For example, the multicast repairinformation may be range information of source symbols (original symbolsof the target file) that need to be repaired.

According to an embodiment of the inventive concept, the network sidemay statistically analyze range information of all symbols lost by UEstransmitting the multicast attempt repair requests during a currentrequest time period, and determine a range of all symbols lost by theUEs as the multicast repair information, namely a largest UE supportedrepair mode. This method is suitable for scenarios where the lost formof the different UEs is uniform.

According to an embodiment of the inventive concept, the network sidemay statistically analyze a range of a predetermined ratio of allsymbols lost by UEs transmitting the attempt requests during the currentrequest time period, e.g., the multicast repair information may besymbols covering the predetermined ratio of all symbols lost by themultiple UEs, namely an optimal UE coverage mode. For example, thepredetermined ratio may be 80%. This method is suitable for scenarioswhere the loss form is a normal distribution.

In this way, by combining with a selection of the predetermined ratio, areasonable repair range may be controlled, and then the amount ofmulticast repair data may be controlled. It can be understood that thelarger the predetermined ratio is, the larger the repair range is, andthe higher the repair success rate is; furthermore, the larger thepredetermined ratio is, the larger the amount of data is. In a specificapplication, it may be combined with the distribution of the lost datato determine which predetermined ratio is used to perform statistics onthe lost symbols.

As an example, the network side may predict the multicast repairinformation through a machine learning multi-classification model. Themodule for determining whether to perform the multicast repair and themodule for determining the multicast repair information may be completedtogether through one machine learning multi-classification model. Aninput of the machine learning multi-classification model may be featurevalues extracted from multicast attempt repair requests received fromthe network side, such as an average number of the lost symbols for eachUE, the number of UEs transmitting the multicast attempt repairrequests, a mean value of the symbol loss distribution set of all UEs,etc., and an output may be the multicast repair information.

For example, Table 1 is a statistical table of the lost symbols of allUEs that have transmitted the multicast attempt repair requests in amulticast area within a request interval. Symbol 0 - Symbol n representnumbers of the symbols in a Block, and UE 0 - UE n represent the UEsthat transmit the multicast attempt repair requests within the requestinterval. Among them, 1 indicates that the symbol of the correspondingnumber is lost, and 0 indicates that the symbol of the correspondingnumber has been received.

TABLE 1 UE\Symbol Symbol 0 Symbol 1 ... Symbol n-1 Symbol n UE 0 0 1 1 0UE 1 1 0 0 1 ... ... ... ... ... ... UE n 0 1 1 1

First, the network side performs feature engineering on data carried inthe received multicast attempt repair requests, and defines 6 Featuresand 3 Labels.

Feature 0: the number of UEs transmitting multicast attempt repairrequests. This feature reflects an occurrence of loss at the macrolevel.

Feature 1: the average number of the lost symbols for each UE. Thisfeature reflects severity of loss.

Feature 2: the mean value of the symbol loss distribution set of allUEs.

Feature 3: a variance of the symbol loss distribution set of all UEs.

Feature 4: a mean value of a set of the number of all UEs that have lostsymbols.

Feature 5: a variance of the set of the number of all UEs that have lostsymbols.

Label 0: do not perform multicast file repair.

Label 1: multicast repair - largest UE supported repair mode, e.g., themulticast repair information includes a range of all symbols lost by allUEs that transmit the multicast attempt repair requests.

Label 2: multicast repair - optimal UE coverage mode, e.g., themulticast repair information includes a range of a predetermined ratioof all symbols lost by all UEs that transmit the multicast attemptrepair requests.

By using online data collection, clustering (such as K-means) iscompleted through a machine learning algorithm, and Labels are manuallymarked based on expert experience as an offline training data source. Amachine learning method such as artificial neural network, supportvector machine, decision tree, etc. may be used to train the machinelearning multi-classification model. When training the model, acombination of binary classifiers may be used to implement theconstruction of a multi-classifier. First, samples are divided into twotypes: no multicast repair and multicast repair, and then the multicastrepair information is divided into the largest UE supported repair modeand the optimal UE coverage mode.

Feature extraction is performed on the data in Table 1 to obtain Feature1 – Feature 5, and Feature 1 – Feature 5 are input to the trainedmachine learning multi-classification model. The multi-classificationmodel outputs any of Label 0, Label 1, or Label 2 according to Feature1-Feature 5.

If the classification model outputs Label 1 or Label 2, the network sidefurther needs to decide the method of the multicast repair, e.g.,whether to repair by a simple repair data packet method or repair by ahybrid repair data packet method.

Among them, in the simple repair data packet method, the network sideonly multicasts repair symbols of the target file to UEs. The repairsymbol is a symbol encoded by the Raptor algorithm. When the number ofsource symbols and repair symbols received by the UE slightly exceedsthe original total number of source symbols, FEC repair may be performedthrough the Raptor algorithm.

In the hybrid repair data packet method, the network side multicastssource symbol and repair symbol corresponding to repair information toUEs.

For example, if the network side determines that most UEs only lose asmall amount of data packets according to the range information of thesymbols lost by each UE, the simple repair data packet method may beadopted. If the network side determines that multiple UEs have morepacket loss in different ranges according to the range information ofthe symbols lost by each UE and the number of UEs that lost each symbol,etc., the hybrid repair data packet method may be adopted. It should benoted that the network side may set different strategies to determinewhich repair data packet method is to be adopted, which is notspecifically limited in the inventive concept.

For example, if the network side determines to use the simple repairdata packet method, it determines the repair symbols according to amultiple greater than a channel transmission packet loss rate, so thatit can ensure that the UE receives enough symbols and then restores anoriginal file through Forward Error Correction (FEC) repair. In thisway, the amount of redundant data is small and the amount of datatransmission can be reduced.

If the network side determines to adopt the hybrid repair data packetmethod, the network side multicasts the source symbol and the repairsymbol corresponding to the repair information to the UEs. In otherwords, if the multicast repair information is all symbols lost by allUEs that transmit the multicast attempt repair requests, the data packettransmitted to the UEs by the network side includes all source symbolsand repair symbols lost by all UEs that transmit the multicast attemptrepair requests. If the multicast repair information includes thesymbols of the predetermined ratio lost by all UEs that transmit themulticast attempt repair requests, the data packet transmitted to theUEs by the network side includes the source symbols and repair symbolsof the predetermined ratio lost by all UEs that transmit the multicastattempt repair requests. This method not only retransmits original lostsource symbols, but also transmits the repair symbols of the originallost data packet, so the transmission redundancy is relatively large,but the Raptor decoding success rate is higher and the speed is faster.

FIG. 4 shows a timing diagram of a file repair method of a UE accordingto an embodiment of the inventive concept. FIG. 4 shows file repair byUEs and a network side, where the network side may be a BM-SC networkelement. The BM-SC network element multicast area includes UE1, UE2,UE3, and UE4.

After the BM-SC receives attempt requests of the UEs, it may performstatistics on the number of requests for each file. If a multicastrepair threshold is not reached, a multicast repair flag is returned tothe UEs as default (e.g., the first feedback message); on the otherhand, if the multicast repair threshold is reached, the multicast repairflag is returned to the UEs as supported (e.g., the feedback message),and FDT or SDP may be selected to return at substantially the same timeand multicast repair preparation is performed at substantially the sametime. After making a multicast repair decision, the BM-SC may select thelargest UE supported repair mode (e.g., take the largest symbol lossrange or number in the UEs), or the optimal UE coverage mode (coveringmore than 90% of the UEs′ loss range) according to statistical analysisof symbol ranges or numbers requested by the UEs during a currentrequest time period. Then, it decides to select the simple repair datapacket method or hybrid repair data packet method, as discussed above.

After UE1-UE4 transmit the multicast attempt repair requests, when themulticast repair flag is received as default, it may be necessary tokeep waiting (such as UE1 in FIG. 4 ). Before the Multicast RepairOffset Time is reached, if an In-band FDT update or SDP update isreceived, the multicast file repair process is performed, like UE2 andUE3; otherwise, the process of operations S106-S109 is performed, likeUE4. If in some extreme scenarios (such as the BM-SC transmitting datapackets with the optimal UE coverage, the source symbols lost by the UEsare not transmitted, and not enough repair symbols are received to makeup), after entering the multicast repair, Forward Error Correction (FEC)repair fails, it will switch to the processes of operations S106-S109,like UE2. Since the multicast repair has been entered previously, theoriginal unicast repair has been cancelled, the unicast repair processneeds to be restarted here, UE2 corresponds to the Back-off Time, andUE4 that directly enters the unicast repair process corresponds to theRandom Time Period.

FIG. 5 shows a block diagram of a file repair device on a user equipment(UE) side according to an embodiment of the inventive concept. The UEreceives a target file multicasted by a network side in a file downloadtransmission (FDT) manner. The device may include a requesting unit 11,a first receiving unit 12, and a repairing unit 13. According to anembodiment of the inventive concept, the requesting unit 11, the firstreceiving unit 12, and the repairing unit 13 may be circuits.

The requesting unit 11 is configured to transmit a multicast attemptrepair request for the target file to the network side in a first timeperiod after determining that the target file needs to be repaired, andthe first time period does not exceed a time period of a Back-off timeof a current session. The first receiving unit 12 is configured toreceive a feedback message transmitted by the network side, and thefeedback message is used to instruct the UE to perform multicast repair.The repairing unit 13 is configured to perform the multicast repair onthe target file in response to the received feedback message.

Alternatively, the first time period may be a time period of an Offsettime of the current session. This ensures that after the network sidemakes a unicast repair decision, the UE may still perform the unicastrepair in time to ensure the timeliness of repairing the target file.

Alternatively, the multicast attempt repair request may carry an attemptflag bit used to inquire the network side whether to perform themulticast repair on the target file. By configuring the attempt flagbit, the multicast attempt repair request may be distinguished from anoriginal repair request, and two repair solutions may be provided at thesame time, so that the accessed network side makes the decision andselection, thus improving compatibility.

Alternatively, the feedback message may carry a flag bit instructing theUE to perform the multicast repair. The flag bit may include a FDTupdate flag instructing the UE to receive repair data of the target filemulticasted by the network side based on the current session, or mayinclude a session description protocol (SDP) update flag instructing theUE to receive repair data of the target file multicasted by the networkside in a new session. By feeding back the flag bit, downlink networktransmission overhead may be minimized. By configuring the FDT updateflag or the SDP update flag, the UE may be clearly indicated how toreceive the repair data.

Alternatively, the first receiving unit 12 may be further configured to:before receiving the feedback message transmitted by the network side,receive a first feedback message transmitted by the network side. Thefirst feedback message is used to instruct the UE to wait for amulticast decision instruction from the network side.

Alternatively, the repairing unit 13 may be configured to: afterperforming the multicast repair on the target file according to thereceived feedback message, if the repair of the target file fails,perform unicast repair of the target file.

FIG. 6 shows a block diagram of a file repair device on a network sideaccording to an embodiment of the inventive concept. The UE receives atarget file multicasted by a network side in a file downloadtransmission (FDT) manner. The device may include a second receivingunit 21, a decision unit 22, and a transmitting unit 23. According to anembodiment of the inventive concept, the second receiving unit 21, thedecision unit 22, and the transmitting unit 23 may be circuits.

The second receiving unit 21 is configured to receive multicast attemptrepair requests for the target file transmitted by UEs including the UE.The decision unit 22 is configured to perform statistics on the receivedmulticast attempt repair requests for the target file to determinewhether to perform multicast repair on the target file before a secondtime period expires, and the second time period is less than a timeperiod of a Back-off time of a current session. The transmitting unit 23is configured to transmit a feedback message to the UEs in a multicastarea if it is determined to perform the multicast repair on the targetfile, and the feedback message is used to instruct the UE to perform themulticast repair on the target file.

Alternatively, the second time period may be a time period of an Offsettime of the current session plus a preset time period. By adding thepreset time period on the basis of an original Offset Time as the secondtime period, a buffer time may be reserved for the network side feedingback the multicast repair decision.

Alternatively, the multicast attempt repair request may carry an attemptflag bit used to inquire the network side whether to perform themulticast repair on the target file.

Alternatively, the feedback message may carry a flag bit instructing theUE to perform the multicast repair. The flag bit includes a FDT updateflag instructing the UE to receive repair data of the target filemulticasted by the network side based on the current session; or theflag bit includes a session description protocol (SDP) update flaginstructing the UE to receive repair data of the target file multicastedby the network side in a new session.

Alternatively, the transmitting unit 23 may be further configured to:before the second time period expires, and if it is determined not toperform the multicast repair on the target file, transmit a firstfeedback message to the UEs in the multicast area. The first feedbackmessage is used to instruct the UE to wait for a multicast decisioninstruction from the network side. By configuring the first feedbackmessage, it is possible to wait before the decision of multicast repairhas not been made instead of directly performing the unicast repair,thus performing the multicast repair first and reducing downlink unicasttraffic. After the second time period expires, if the feedback messagefor the multicast repair is still not received, the original repairprocess may be entered and the unicast repair is performed, achievingsmooth unicast and multicast repair switching and ensuring a final filerepair success rate, which has better compatibility and robustness.

Alternatively, the multicast attempt repair request may further carrytarget file information lost by the UE.

FIG. 7 shows a block diagram of a decision unit according to anembodiment of the inventive concept. The decision unit 22 of FIG. 6 mayinclude a statistical subunit 221 and a determining subunit 222. Thestatistical subunit 221 is configured to perform statistics on the losttarget file information in the received multicast attempt repairrequests to generate statistics results if it is determined to performthe multicast repair on the target file, before the second time periodexpires. The determining subunit 222 is configured to determinemulticast repair information based on the statistics result. Bydetermining reasonable repair information for the multicast repairaccording to the statistics result of the lost target file information,it is possible to reduce the amount of repair data transmitted whilemeeting the repair requirements as much as possible, thus reducing theamount of downlink data. According to an embodiment of the inventiveconcept, the statistical subunit 221 and the determining subunit 222 maybe circuits.

Alternatively, the determining subunit 222 may be configured todetermine range information of all symbols lost by the UEs that transmitthe multicast attempt repair requests in a current request time periodas the multicast repair information, which is suitable for a scenariowhere the loss form of different UEs is uniform; or the determiningsubunit 222 may be configured to determine range information of apredetermined ratio of all symbols lost by the UEs that transmit themulticast attempt repair requests in a current request time period asthe multicast repair information, which is suitable for a scenario wherethe loss form of different UEs is a normal distribution. This solutionsatisfies the repair needs of different lost form scenarios.

The file repair method of the user equipment (UE) according toembodiments of the inventive concept may be written as a computerprogram and stored on a computer readable storage medium. When thecomputer program is executed by a processor, the file repair method ofthe user equipment (UE) described above may be implemented.

Examples of computer-readable storage media include: Read Only Memory(ROM), Random Access Programmable Read Only Memory (RAPROM),Electrically Erasable Programmable Read Only Memory (EEPROM), RandomAccess Memory (RAM), Dynamic Random Access Memory (DRAM), Static RandomAccess Memory (SRAM), flash memory, non-volatile memory, CD-ROM, CD-R,CD+R, CD-RW, CD+RW, DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM,BD-ROM, BD-R, BD-R LTH, BD-RE, Blu-ray or optical disk storage, HardDisk Drive (HDD), Solid State Drive (SSD), card storage (such asmultimedia cards, secure digital (SD) cards, or extremely fast digital(xD) cards), magnetic tapes, floppy disks, magneto-optical data storagedevices, optical data storage devices, hard disks, solid state disks, orany other devices that are configured to store computer programs and anyassociated data, data files, and data structures in a non-transitorymanner, and provide the computer programs and any associated data, datafiles, and data structures to a processor or computer so that theprocessor or computer can execute the computer programs. In one example,the computer programs and any associated data, data files, and datastructures are distributed on a networked computer system, so that thecomputer programs and any associated data, data files, and datastructures are stored, accessed, and executed through one or moreprocessors or computers in a distributed manner.

The file repair method of the user equipment (UE) according toembodiments of the inventive concept may be implemented in the userequipment. For example, the user equipment may include: at least oneprocessor and at least one memory, where the at least one memory storescomputer executable instructions, and the computer-executableinstructions, when executed by the at least one processor, implement thefile repair method of the user equipment (UE) described in the aboveembodiments of the inventive concept.

The file repair method of the UE according to embodiments of theinventive concept may be implemented in a network side device. Forexample, the network side device may include: at least one processor andat least one memory, where the at least one memory storescomputer-executable instructions, and the computer executableinstructions, when executed by the at least one processor, implement thefile repair method of the UE described in the above embodiments of theinventive concept.

The file repair method of the UE according to embodiments of theinventive concept combines characteristics and advantages of Raptoritself, and proposes a file repair solution mainly based on multicastrepair. Through a designed signaling transmission strategy and amulticast decision model based on machine learning, inefficiency andincomplete repair problems in the existing unicast-first repair schememay be reduced or eliminated. The embodiments of the inventive conceptare backward compatible with the file unicast repair solution of the R14version of eMBMS 26.346, and support smooth switching of unicast andmulticast repair. In the multicast repair solution, unicast repair istaken as a supplementary solution under special conditions, so thatnetwork bandwidth resources are greatly saved while repair capacity isguaranteed.

As described above, the file repair method for the UE according toembodiments of the inventive concept transmits the multicast attemptrepair request for the target file to the network side in advance, sothat the network side may collect the repair request for the target filefrom the UE in advance, and then may quickly decide whether to performmulticast repair. Especially in the case that the multicast repair isrequired, the multicast repair is performed on the target file first.The embodiments of the inventive concept are also backward compatiblewith the original file repair strategy, e.g., when the network sidedecides that it is not necessary to enable the multicast repair, or whenthe multicast repair fails, the original repair process will beperformed, and thus it is possible to focus on the multicast repair andsupplement with the unicast repair. On one hand, smooth unicast andmulticast repair switching may be achieved, which ensures a final filerepair success rate and has better compatibility and robustness. On theother hand, most UEs may only make one uplink request, and only aminority of UEs in extreme cases will enter the unicast repair process,which may reduce downlink unicast traffic, reduce the dependence on alarge number of file repair servers, and greatly reduce the consumptionof bandwidth and software and hardware resources.

Although the inventive concept has been shown and described withreference to embodiments thereof, it will be understood by those ofordinary skill in the art that various modifications in form and detailsmay be made thereto without departing from the spirit and scope of theinventive concept as set forth by the appended claims.

1. A file repair method for a user equipment (UE) configured to receivea target file multicasted by a network side in a file downloadtransmission (FDT) manner, the method comprising: transmitting, by theUE, a multicast attempt repair request for the target file to thenetwork side in a first time period after determining that the targetfile needs to be repaired, wherein the first time period does not exceeda time period of a Back-off time of a current session; receiving, by theUE, a feedback message transmitted by the network side, wherein thefeedback message instructs the UE to perform multicast repair; andperforming, by the UE, the multicast repair on the target file inresponse to the received feedback message.
 2. The method of claim 1,wherein the first time period is a time period of an Offset time of thecurrent session.
 3. The method of claim 2, wherein the multicast attemptrepair request carries an attempt flag bit to inquire the network sidewhether to perform the multicast repair on the target file.
 4. Themethod of claim 1, wherein the feedback message carries a flag bit toinstruct the UE to perform the multicast repair, the flag bit comprisesa FDT update flag or session description protocol (SDP) update flag, theFDT update flag instructs the UE to receive repair data of the targetfile multicasted by the network side based on the current session, andthe SDP update flag instructs the UE to receive repair data of thetarget file multicasted by the network side in a new session.
 5. Themethod of claim 1, wherein before the UE receives the feedback messagetransmitted by the network side, the method further comprises:receiving, by the UE, a first feedback message transmitted by thenetwork side, wherein the first feedback message instructs the UE towait for a multicast decision instruction from the network side.
 6. Themethod of claim 1, wherein after the UE performs the multicast repair onthe target file in response to the received feedback message, the methodfurther comprises: performing, by the UE, unicast repair of the targetfile if the multicast repair of the target file fails.
 7. A file repairmethod for a first user equipment (UE) configured to receive a targetfile multicasted by a network side in a file download transmission (FDT)manner, the method comprising: receiving, by the network side, multicastattempt repair requests for the target file transmitted by UEs includingthe first UE; performing, by the network side, statistics on thereceived multicast attempt repair requests for the target file todetermine whether to perform multicast repair on the target file beforea second time period expires, wherein the second time period is lessthan a time period of a Back-off time of a current session; andtransmitting, by the network side, a feedback message to the UEs in amulticast area if it is determined to perform the multicast repair onthe target file, wherein the feedback message instructs the first UE toperform the multicast repair on the target file.
 8. The method of claim7, wherein the second time period is a time period of an Offset time ofthe current session plus a preset time period.
 9. The method of claim 7,wherein the multicast attempt repair requests carry an attempt flag bitto inquire the network side whether to perform the multicast repair onthe target file.
 10. The method of claim 7, wherein the feedback messagecarries a flag bit to instruct the first UE to perform the multicastrepair, the flag bit comprises a FDT update flag or a sessiondescription protocol (SDP) update flag, the FDT update flag instructsthe first UE to receive repair data of the target file multicasted bythe network side based on the current session, and the SDP update flaginstructs the first UE to receive repair data of the target filemulticasted by the network side in a new session.
 11. The method ofclaim 7, wherein before the second time period expires, if the networkside determines not to perform the multicast repair on the target file,the network side transmits a first feedback message to the UEs in themulticast area, and the first feedback message instructs the UEs to waitfor a multicast decision instruction from the network side.
 12. Themethod of claim 7, wherein the multicast attempt repair requests furthercarry target file information lost by the UEs, and before the secondtime period expires, if the network side determines to perform themulticast repair on the target file, the method further comprises:performing statistics on the target file information in the receivedmulticast attempt repair requests to generate a statistics result; anddetermining multicast repair information based on the statistics result.13. The method of claim 12, wherein determining the multicast repairinformation based on the statistics result comprises: determining rangeinformation of all symbols lost by the UEs that transmit the multicastattempt repair requests in a current request time period as themulticast repair information; or determining range information of apredetermined ratio of all symbols lost by the UEs that transmit themulticast attempt repair requests in the current request time period asthe multicast repair information.
 14. A file repair device for a userequipment (UE) configured to receive a target file multicasted by anetwork side in a file download transmission (FDT) manner, the devicecomprising: a requesting circuit configured to transmit a multicastattempt repair request for the target file to the network side in afirst time period after determining that the target file needs to berepaired, wherein the first time period does not exceed a time period ofa Back-off time of a current session; a receiving circuit configured toreceive a feedback message transmitted by the network side, wherein thefeedback message instructs the UE to perform multicast repair; and arepairing circuit configured to perform the multicast repair on thetarget file in response to the received feedback message.
 15. The deviceof claim 14, wherein the first time period is a time period of an Offsettime of the current session.
 16. The device of claim 15, wherein themulticast attempt repair request carries an attempt flag bit to inquirethe network side whether to perform the multicast repair on the targetfile.
 17. The device of claim 14, wherein the feedback message carries aflag bit to instruct the UE to perform the multicast repair, the flagbit comprises a FDT update flag or a session description protocol (SDP)update flag, the FDT update flag instructs the UE to receive repair dataof the target file multicasted by the network side based on the currentsession, and the SDP update flag instructs the UE to receive repair dataof the target file multicasted by the network side in a new session. 18.The device of claim 14, wherein the receiving circuit is furtherconfigured to: before receiving the feedback message transmitted by thenetwork side, receive a first feedback message transmitted by thenetwork side, wherein the first feedback message instructs the UE towait for a multicast decision instruction from the network side.
 19. Thedevice of claim 14, wherein the repairing circuit is configured to:after performing the multicast repair on the target file in response tothe received feedback message and if the multicast repair of the targetfile fails, perform unicast repair of the target file. 20-30. (canceled)